<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
            #fa {
                position: absolute;
            }
    </style>
</head>
<body>
<div id="gf">
    <div id="fa">
        <div id="son"></div>
    </div>
</div>
</body>
</html>
<script>
    var son = document.getElementById("son");
    //alert(son.parentNode.id);
    alert(son.offsetParent.tagName);  // tagName标签的名字